The very first opinion is that Tezxas is misspelled word
Texas. Not exactly.

TI 89 is a new machine. Although software for it grows
rapidly, it still can not be compared with software base for
older computers. And, while on desktop area incompatibility
vanished (you have PC with some operating systems or Macintosh
with MacOS), every calculator, even from the same producer is
still own story.

My first computer was ZX Spectrum. I bought it in 1984. The
characteristics seem today funny: 48 kilobytes of RAM, tape
recorder as memory unit, CPU Z80 at 3.5 MHz, graphic 256x192
pixels in 16 color (group of 64 pixels must be in one of two
colors), beeper sound generated by CPU, rubber keyboard ...

But, such machine was ideal for introduction to computers
world. With start price of 100 GBP, it was enough cheap even for
East Europe, or Latin America. Unlike it major opponent Commodore
64 , wich was better machine for users of commercial games and
utility programs, ZX Spectrum had BASIC ideal for easy writing
your own software. Soon appeared a dozens of commercial and
freeware games, programming languages, word processors,
spreadsheets ... My estimation is that there were about 20000
programs (including those published in newspapers all over the
world). Today on Internet there are about 8000 available programs
for ZX Spectrum.

The software for ZX Spectrum after 1986 was reduced to games,
and in 1992 even games stopped with releasing.

My later computers were Casio fx-8000, AT-286, 486-SX, Pentium
100 and TI-89, but ZX Spectrum was my first love.

Well, starting from 1990, Spectrum moved to virtual computer.
Almost everyone replaced ZX Spectrum with PC, Amiga or Atari ST,
but those machines were enough powerful to execute emulators at
machine code level. First emulators were written, and interest
for ZX Spectrum reappeared. The games are now written for
emulated Spectrums, and in Russia the modernized versions of ZX
Spectrum are still produced.

Zeljko and me wrote one excelent emulator of ZX Spectrum for
MS DOS computers. It is called Warajevo ZX Spectrum
emulator because it was written mainly in Sarajevo during
Bosnian war.

OK, OK, Stop with history, What is TeZXas?

The same day I have bought TI-89 I started to write ZX
Spectrum emulator for it. It was a challenge, this was my first
TI-89 program, and first Motorola 68000 assembly program! And, I
was limited to 10 MHz machine with only 180 KB available memory
and small screen.

The result of symbiosys of Texas Instruments TI 89 and
Sinclair ZX Spectrum is Tezxas, the emulator. Now, TI89 can start
almost all games originally written for ZX Spectrum.

Later I ported Tezxas to TI92+. The bigger screen was big
advantage.

Tezxas is not perfect emulator. Some games are slow, screen is
sometimes hardly visible, keyboard layout is strange. But keep in
mind that TI89 is the most limited machine that emulates ZX
Spectrum 48K at machine code level, and that perfomances of
Tezxas are better than perfomances of some emulators on Pentium
133.